With the recent trend toward size reduction in electronic appliances, secondary batteries are increasingly required to have a higher capacity. Attention is hence focused on lithium secondary batteries, which have a higher energy density than nickel-cadmium batteries and nickel-hydrogen batteries.
Lithium secondary batteries are used in various applications because they are high-capacity secondary batteries. In these applications, however, the lithium secondary batteries are mainly used as batteries of relatively small sizes as in, e.g., portable telephones. In the future, the batteries are expected to be used in a wider range of applications as large batteries for motor vehicles, etc. Although output is especially required of large batteries, mere enlargement of conventional small batteries results in insufficient performances. Various improvements in battery materials for an output improvement have been proposed (see, for example, patent documents 1 to 25 and non-patent document 1). However, a sufficient output has not been obtained so far, and a further improvement is desired.    Patent Document 1: JP-A-2005-071749    Patent Document 2: JP-A-2005-123180    Patent Document 3: JP-A-2001-206722    Patent Document 4: JP-A-2003-267732    Patent Document 5: JP-A-2001-015108    Patent Document 6: WO 2003/34518    Patent Document 7: JP-A-11-067270    Patent Document 8: JP-A-61-168512    Patent Document 9: JP-A-6-275263    Patent Document 10: JP-A-2000-340232    Patent Document 11: JP-A-2005-235397    Patent Document 12: JP-A-11-031509    Patent Document 13: JP-A-3-055770    Patent Document 14: JP-A-2004-071458    Patent Document 15: JP-A-2004-087459    Patent Document 16: JP-A-10-270074    Patent Document 17: JP-A-2002-075440    Patent Document 18: JP-A-10-270075    Patent Document 19: JP-A-8-045545    Patent Document 20: JP-A-2001-006729    Patent Document 21: JP-A-10-050342    Patent Document 22: JP-A-9-106835    Patent Document 23: JP-A-2000-058116    Patent Document 24: JP-A-2001-015158    Patent Document 25: JP-A-2005-306619    Non-Patent Document 1: J. Electrochem. Soc., 145, L1 (1998)